Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. The high vapor pressure results from a low boiling point, and this causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. VOCs are emitted as gases from various solids or liquids, and concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors. Some materials from which VOCs can be emitted include paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions. Fuels are also made up of organic chemicals. All of these products can release organic compounds while in use and, to some degree, when stored.
Many VOCs are potentially dangerous to human health or cause harm to the environment. VOCs may have short-term and/or long-term adverse health effects. VOCs are typically not acutely toxic, but instead may have compounding long-term health effects. Some of the health effects of VOCs include eye, nose, and throat irritation, headaches, loss of coordination, nausea, liver, kidney, and central nervous system damage and cancer. Because the concentrations of VOCs are typically low and exposures usually occur over extended periods of time, symptoms may be slow to develop.
Accurate and sensitive detection of VOCs is critical because of the destructive nature of VOCs to human health and the environment, and because they are typically present in low concentrations. VOCs in the environment or certain atmospheres can be detected based on different principles and interactions between the organic compounds and the sensor components. Electronic devices may be capable of detecting concentrations of parts-per-million but are generally expensive. Other types of sensors may be less sensitive and/or have slow response times. In many cases, organic vapor sensors are designed to detect particular vapors, but providing a response to a variety of organic vapors may be more useful. Some exemplary uses of this nature may include indoor detection and leak or spill detection. Some organic vapor sensors function on the basis of fluorescence ‘turn-off’ upon exposure to organic vapors. These ‘turn-off’ sensors may exhibit a decrease in detection sensitivity due to background intensity. It is therefore desirable to provide a detector that can act as a fluorescence ‘turn on’ vapor sensor having high sensitivity and fast response for a broad range of VOCs.